Sulfonylurea receptors (SURs) provide a unique link between cardiac metabolism and excitability. Previous efforts on this project have demonstrated that both SUR1 and SUR2 genes are expressed in the heart, with spatial and pathological variability in different regions. Because these subunits confer different metabolic and pharmacologic sensitivities to KATP channels, this realization means that cardiac KATP channel activation may vary regionally and with disease state. Additional studies suggest that differentially spliced versions of the proteins may be expressed in the heart and confer differential functional consequences. The development of novel cell biological tools and transgenic animals have allowed us to generate extensive preliminary data that lead us to propose experiments using biochemical, cell biological and physiological approaches to reach a full understanding of the nature and role of SUR subunit variation in the heart. They are motivated by our discovery of differential subunit expression and consequent functional differences within the mouse heart based on analysis of genetically modified animals, and encompass both mechanistic studies of expression control, and studies of the functional consequences in model systems and human hearts.